ETC용 전파흡수체의 개발에 관한 연구

Abstract

According to the increase of occupation density of microwave frequency band in use, electromagnetic environments become congested extensively. It often cause TV ghost, radar false echoes by wave reflection from adjacent constructions. Especially, in the area where strong reflectors, such as high building, steel tower, iron bridge, etc., exist around radio wave facilities, the performance of such apparatus often deteriorates due to multipath interference between direct wave and those reflected from these constrictions. Thus, to Countermeasure the electromagnetic wave interference, the radiated electromagnetic fields of digital electronic products must be measured and must not exceed the specified levels.

In addition, the increase of new devices Electromagnetic Interference (EMI) or Electromagnetic Susceptibility (EMS) problems. Therefore, the international or local regulations suggest certain standards for EMI / EMS.

These problems can be eliminated by using EM wave absorbers. It is important to develop absorbing material for preventing EMI.

MnZn-ferrite or Carbon is useful as a microwave absorbing material because their electric and magnetic loss contribute to the microwave absorption efficiently.

This thesis deal with basic research for development of EM wave absorbers in sheet type for Electronic Toll Collection (ETC), By controlling the MnZn-ferrite ratio, the Carbon ratio, the thickness, the kind of binders, the milling time, EM wave absorbers were prepared and examined. Matching frequency shifts toward higher with decreasing thickness of the absorber, and absorption ability controlled by adjusting MnZn-ferrite and Carbon amount. MnZn-ferrite and Carbon composite microwave absorbers mixed with CPE were prepared at 70℃ in temperature. The fabricated EM wave absorbers show a reflection coefficient - 23 dB at 5.8 GHz in thickness of 3.3 mm by transmission line method. In case incident wave angle was 15°, the EM wave absorber was observed -17 dB at 5.8 GHZ with the thickness of 3.38±0.05 mm, in case incident wave angle was 30°, the EM wave absorber was observed -14 dB at 5.8 GHZ with the thickness of 3.38±0.05 mm, in case incident wave angle was 45°, the EM wave absorber was observed -12 dB at 5.8 GHZ with the thickness of 3.38±0.05 mm by free space method.